{
  "abstract": "Introduction Large brain arteriovenous malformations (AVMs) (>3 cm) are rare and carry a high risk of rupture. Their size and diffuse architecture preclude safe microsurgical resection. Radiosurgery or embolization alone may be insufficient. Adjunctive embolization prior to radiosurgery remains controversial.Objective Given our previously reported high obliteration rates with this combined approach, we sought to update our institutional experience and examine discrepancies in outcomes reported in the literature.Methods Large AVMs treated from 1997–2023 at Washington University in St. Louis were retrospectively reviewed. Across the study period, the primary difference observed was embolic agent selection. Patients treated with n-butyl cyanoacrylate (n-BCA) were compared with Onyx (Medtronic) prior to Gamma-Knife radiosurgery (GKRS). Group comparisons were performed using univariate tests and modified Poisson regression (p < 0.05).Results Among 40 AVMs, 22 were treated with Onyx (median treatment year 2017, IQR 2012–2020) and 18 with n-BCA (2001, IQR 2001–2013). AVMs in the Onyx group were larger at baseline (39 vs. 18mL; p = 0.014), while patient age, Spetzler-Martin grade, and lesion location were comparable. Despite treating larger AVMs, the Onyx group underwent a similar number of embolization procedures. Greater nidus volume reduction was achieved with Onyx (81% vs. 60%, p = 0.0085), resulting in smaller post-embolization targets for radiosurgical planning (12.5 vs. 18.2mL, p = 0.03). Permanent neurological deficits were less frequent (4% vs. 17%). GKRS parameters, complication rates, and follow-up duration were similar. Final obliteration rates were lower in the Onyx cohort (56% vs. 93%, p = 0.008). In crude modified Poisson regression adjusting for known obliteration confounders, only embolic agent remained significant. Recanalization and imaging artifact were assessed but not observed.Conclusion Despite more aggressive embolization and smaller treatment volumes, Onyx use was associated with lower radiosurgical obliteration rates in volume- and follow-up-matched AVMs.Disclosures H. Hallak: None. J. Yuan: None. G. Zipfel: None.Abstract E-062 Figure 1",
  "authors": [
    {
      "affiliations": [
        "Neurosurgery, Washington University in St. Louis, Saint Louis, MO"
      ],
      "name": "H Hallak"
    },
    {
      "affiliations": [
        "Neurosurgery, Washington University in St. Louis, Saint Louis, MO"
      ],
      "name": "M Connor"
    },
    {
      "affiliations": [
        "Neurosurgery, Washington University in St. Louis, Saint Louis, MO"
      ],
      "name": "J Yuan"
    },
    {
      "affiliations": [
        "Neurological Surgery, Washington University School of Medicine, St. Louis, MO"
      ],
      "name": "J Osbun"
    },
    {
      "affiliations": [
        "Neurosurgery, Washington University in St. Louis, Saint Louis, MO"
      ],
      "name": "G Zipfel"
    }
  ],
  "title": "E-062 Onyx embolization compromises gamma-knife dosimetry in multimodal management of large AVMs",
  "uid": "338d3a17-90aa-54a2-a08f-68015cb1442e"
}